It is important in breeding of aquatic life to quickly supply oxygen required for breathing in a breeding liquid and to quickly remove unnecessary carbon acid gas from the breeding liquid. Such dissolving of the gas into the liquid or removal (evaporation) of the gas from the liquid relies upon the size of the contact surface area between the gas and the liquid. If the contact surface area is constant, movement of ht liquid, that is, stirring of the liquid increases the contact surface area, so that dissolving or evaporation quickly occurs. The invention is directed to stagnate or accumulate the gas into the liquid in a plurality of separated manners thereby increasing the contact surface area between the gas and the liquid in a three-dimensional manner and, further, to stir the liquid by a motor located centrally thereby rapidly increasing the contact effect.